This invention relates to wireless communication systems and, more particularly, to the management of system resource parameters as a function of a quality of service parameter.
Wireless communication systems allow the transmission of information signals between a mobile user and a fixed based station. The base station will typically be interconnected with one or more landline communications networks. Both analog (first generation) and digital (second/third generation) systems have been developed to transmit information signals over communication channels linking the mobile user with landline networks. Digital methods tend to afford several advantages over analog systems, including improved immunity to channel noise and interference, increased capacity, and encryption for secure communications.
First generation wireless systems were primarily directed to voice communication, but the digital technology of second and third-generation systems provides support for both voice and data applications. Several modulation/coding arrangements have been developed, such as frequency division multiple access (FDMA), time division multiple access (TDMA) and code division multiple access (CDMA), to increase the number of users that can access a wireless network. CDMA systems are more immune to multi-path distortion and co-channel interference than FDMA and TDMA systems and reduce the burden of frequency/channel planning that is common with FDMA and TDMA systems.
The base stations of a wireless network manage a variety of resources in the establishment of communications links with their associated mobile users. Among those resources are output power and data rate. Output power and data rate are proportionally relatedxe2x80x94the output power necessary to establish or maintain a link with a user increasing as the data rate increases. This increase in output power with increasing data rate is required to maintain the output energy per bit at a constant level. In the management of power output, a base station must balance the transmission needs of its users, individually and collectively, against inter-channel interference among the served mobile users, as well as constraints in respect to total output power for the base station.
Thus, upon a request for entry to the wireless network by a user, the base station must evaluate the user""s data rate and power demands against the current user environment and power demands. As the user environment approaches the total system capacity, the base station may delay the entry of a user onto the system to prevent overloading the output power capability of the base station.
In a communications system utilizing power control, the allocation of the available RF power is usually dictated by a required Frame Error Rate (FER), with the power control system having a feedback mechanism for adjusting power to maintain the required FER under varying channel conditions. Thus, for a given required FER, the output power will vary depending on the difference between the required FER and the FER experienced due to the channel. The instantaneous Eb/Io ratio (essentially, the digital signal-to-noise ratio) for the channel is controlled by the excursion around that set point in the inner loop of the power control system. Once a target FER is set, the power control system operates to dynamically allocate the RF power to overcome channel fades and interference in order to maintain the experienced FER within a tolerable deviation from the required FER.
For voice calls, FERs are usually set between 1% and 2% to meet a required Merit of Service (MoS) parameter. Data communication applications, on the other hand, can generally accept a somewhat higher FER, but the selected FER must satisfy Quality of Service criteria for such applications. There is a need to provide an efficient allocation of wireless system resources among a variety of users and user application requirements.
A method is provided for intelligent utilization of the power and system resources in a wireless communication system in respect to an allocation of such resources to and among a plurality of users. In particular, the invention provides dynamic allocation of power and system resources in proportion to user application requirements such as to achieve optimum resource allocation in a wireless system.
The methodology of the invention operates to determine an allocation of wireless transmission resources to each user application served by the wireless system in a manner to optimize transmission resources while meeting required QoS criteria for the served user application. After all user applications have been provided a transmission resource allocation in this manner, the total allocation of transmission resources is determined and compared with a ceiling transmission resource level for the wireless system. A portion of the difference between the ceiling and currently allocated transmission resource levels is then made available, according to the method of the invention, to the served user applications in proportion to the initial allocation provided each user application.
In a preferred embodiment of the invention, the determination of an initial optimum resource allocation for each user application is performed in accordance with the multi-layer resource management methodology disclosed in the companion cross-referenced application, Ser. No. 09/568,666, designated Lu 5-6-6. According to that methodology, performance characteristics for a user application under consideration and of the wireless channel are determined and stored in the form of a set of tables or corresponding curves (or mathematical equivalents thereof). Data points on those curves are then determined which correspond with a required performance parameter for the user application under consideration (e.g., data throughput). Those data points from the application performance characteristic curves are then mapped to corresponding data points on performance characteristic curves for the physical channel. From that mapping, an FER and a data rate are selected to optimize system power allocation in respect to the data throughput requirement for the application and the characteristics of the selected channel.
After the resource allocation for each user in the system is determined according to a procedure such as that just described, the total resource allocation for all users is determinedxe2x80x94that total allocation representing radio resource utilization for the wireless system. That total resource allocation is then compared with the maximum radio transmission resource available for the wireless system and a portion of the difference between those values is established for use in a xe2x80x9cbonusxe2x80x9d distribution process. The bonus distribution process operates to distribute the available resource loading xe2x80x9ccreditxe2x80x9d to minimize inter-user interference for a maximized aggregated throughput in the system.
With the bonus process of the invention, the available resource loading remaining after making resource allocations directed to achieving required FER/QoS requirements for served users will be distributed to the users in proportion to their initial allocations, thereby increasing utilization for a system that is not fully loaded. A user receiving a bonus resource allocation pursuant to this procedure will be allocated increased transmission power, which will enable the completion of the transmission for a given data file at an earlier time, thereby making system resources available for another user application during that freed-up time increment.